(a) Field of the Invention
The present invention relates to a method of forming multiple copies from one and the same electrostatic latent image, and particularly it relates to an improvement of the dry developer for use in said method.
(B) Description of the Prior Art
There have been known a variety of methods for forming multiple copies by repeating the process of developing an electrostatic latent image formed on the insulating surface of an electrophotographic insulating material such as an electrophotographic sensitive material which consists of a support and a photoconductive layer formed thereon, an electrostatic recording material which consists of a support and a dielectric layer formed thereon, etc. with a dry developer and the process of transferring the thus developed image onto a transfer sheet in succession without erasing said latent image (cf. Japanese Patent Publication Nos. 432/1967, 30233/1969 and 7789/1971, etc.). However, according to these known methods, there can be obtained no more than about 15-20 copies suitable for practical use. In other words, when the processes of developing and transferring are repeated, the portions of the image particularly the portions corresponding to letters and lines therein tend to become thin gradually and be erased in the end.